Many packaging applications, especially food packaging, require or benefit from the use of bags made from various thermoplastic materials and structures.
These bags are commonly used in large scale meat processing and/or packaging systems where production speed and efficiency are important. Bags to be used in these systems can be provided in a roll, with adjoining bags connected by a transverse line of serrations or perforations.
At the loading station of a conventional system, each bag can be opened and then loaded with an article such as a fresh red meat subprimal or smoked and processed meat, poultry, cheese, or other perishable food product, or other product.
Where rolls of serrated bags are employed, it is beneficial to provide a way of dispensing each bag an appropriate distance as it feeds from the selected roll.
One way of accomplishing this is the use of a pre-printed registration mark on each bag.
One disadvantage of using printed registration marks is that an additional operation is required in manufacturing the roll of serrated bags. The printed registration marks must be printed in sequential fashion on each of the series of bags. This would add cost to the roll of bags, and would increase the process time in producing such bags. Also, bags are sometimes printed “on site” i.e. at the location where the bags are sequentially dispensed and loaded with a meat or other product. Pre-printing registration marks on each bag, and then printing additional indicia or codes on each bag at the location where the bags are processed and loaded, is inefficient.
One method of registering rolled serrated bags without the use of print marks, has been the use of a “speed bump” device. As a web of bags is advanced from the roll of serrated bags, this device takes advantage of the fact that a seal on each bag is thicker than the unsealed film on either side of the seal. Each seal can be sensed by the rotary displacement of a lever arm around a pivot point due to the action of each seal displacing a roller away from a fixed member, as the web of bags is advanced across the fixed member. Sensing the motion of the lever arm is accomplished with a proximity switch. A registration signal is generated as each seal passes the fixed point.
Unfortunately, this method would not be consistently reliable if patch bags were to be used in the packaging process. Patch bags, for example those supplied by Sealed Air Corporation under the trademark TBG™, include a seal in the primary bag material, but also a patch on at least a portion of at least one ply of the bag. Patch bags, and methods of making them, are described in U.S. Pat. No. 4,770,731 (Ferguson), U.S. Pat. No. 6,287,613 (Childress et al.), U.S. Pat. No. 6,383,537 (Brady et al.), U.S. Pat. No. 6,254,909 (Williams et al.), U.S. Pat. No. 5,545,419 (Brady et al.), U.S. Pat. No. 6,270,819 (Wiese), U.S. Pat. No. 6,790,468 (Mize et al.), U.S. Pat. No. 6,663,905 (Ennis et al.), U.S. Pat. No. 6,296,886 (DePoorter et al.), U.S. Pat. No. 5,534,276 (Ennis), U.S. Pat. No. 4,704,101 (Schirmer), U.S. Pat. No. 5,020,922 (Schirmer), U.S. Pat. No. 6,228,446 (Moffitt), U.S. Pat. No. 6,884,480 (Bradfute et al.), U.S. Pat. No. 5,376,394 (Dudenhoeffer et al.), U.S. Pat. No. 6,171,627 (Bert et al.), U.S. Pat. No. 6,206,569 (Kraimer et al.), U.S. Pat. No. 6,749,910 (Georgelos et al.), and U.S. Pat. No. 6,777,047 (Tatarka et al.); US Patent Application Publication Nos. US 2003/0175390 (Oberle), 2003/0021870 (Pollok et al.), and 2004/0118735 (Mize et al.); and EP 1095765 A2 (Cryovac, Inc.), EP 1095874 A2 (Cryovac, Inc.), and WO 98/45187 (Cryovac, Inc.); all of the above incorporated herein by reference in their entirety.
The patch of a patch bag would result in a raised portion of the bag in the area of the patch. The configuration of the bag would be such that the “speed bump” methodology could not be totally relied on, because the sensor may variously be reacting to e.g. the bag seal, the front (downstream) end of the patch located on the bag, or the rear (upstream) end of the patch located on the bag, depending on the particular patch bag configuration.
It is therefore desirable to provide a system and method for sensing and registering serrated bags drawn sequentially from a roll, or otherwise provided sequentially, that does not rely on pre-printed registration marks, or on a device that detects the seal area of each bag in a series of bags by displacement of a lever arm.